To make it easier to collaborate during Hangouts video calls, Google enabled the sharing of links to any Drive file directly from the chat window. Shared links will show a preview of the file right in the chat message, even when other participants don’t have their chat window open. Clicking on the link will open the file in a different browser tab so you can conveniently work on it in full view.
To share a link from Drive during a Hangouts video call, click on the Chat icon and then click the Google Drive picker icon from within the chat window.
Note: this feature will replace the Google Drive Hangouts app, which will no longer be available as of December 15th, 2014.
Rapid release and Scheduled release
Reference by www.google.com